Exploring new synthetic strategies in the development of a chemically activated Ru-based olefin metathesis catalyst

Abstract

The objective of this work was to develop an industrially relevant olefin metathesis initiator, which circumvents the expensive, patent protected, often cumbersome preparative routes via Grubbs benzylidene complexes. Upon coordination of a Schiff base ligand to a second-generation ruthenium allenylidene complex, the formation of three catalyst isomers was observed. The major isomer was successfully isolated, and tested in a few olefin metathesis reactions. Acids such as HCl and HSiCl₃ were found to boost the metathesis reaction but the in situ formation of a neutral Ru carbyne complex restricted the catalytic capacity. Using the Lewis acid PhSiCl₃, the formation of a carbyne species was avoided, and turnover numbers up to 30 000 were reached in the ring-opening metathesis polymerisation of cycloocta-1,5-diene.